Sparking plug



June 14, 1938. L. GRAF smmxme PLUG Filed April 1, 1937 Inventor." [.60 Grf P P Afiorne Y.

Patented June 14, 1938 SPARKING PLUG Leo Graf, OoIogne-Bickendorf, Germany, assignor to Karl Werth, Berlin, Germany Application April 1, 1937, Serial No. 134,374 In Germany February 17, 1937 5 Claims. (Cl. l23169) This invention relates to sparking plugs the chief object being to provide a more eflicient sparking plug than heretofore.

A further object is to provide a construction 5 of plug in which particles of oil are substantially prevented from coming into contact with the electrodes.

A further object is to provide an extension chamber for the gases in one or each of the electrodes, said gas extension chamberbeing at a higher pressure than the cylinder chamber during the compression stroke.

In acordance with the present invention a sparking plug comprises a plug body, an insulator body, a plurality of electrodes, an expansion chamber fora portion of the gases and a gas extension chamber provided in one or each of said electrodes. Said gas extension chamber may, therefore, be provided in the cent al electrode, in the mass electrode, or electrodes, or in both the central electrode and the mass electrode, or electrodes.

In order that the invention may be more clearly understood reference will nowbe made to the accompanying drawing which shows by way of example preferred embodiments thereof.

In the drawing:-

Figure 1 is a longitudinal section of the ignition p Figure 2 shows the central electrodeand the mass electrode, the central electrode being reelectrode 2 which, as shown in Figure, 2, is pro- 1 vided at its lower end with a hollow chamber 2a.

At the upper end the central electrode 2 engages with the internal screwthread of a headpiece 3, provided with cooling 'ribs, on the screwed spindle 3a of which there is applied the cable securing nut. At the lower end the central electrode 2 is provided with a collar 4 which presses against the under surface of the insulator foot.

By means of a flanged nut 5 the insulator body is secured in the plug body, whilst a copper ring 1 is fitted between the insulator and the flanged nut. Underneath the headpiece 3, provided with the screw thread, there is provided a cup-shaped cap l0 and between the cap and the upper. end of the insulator there is located a spring H or a device having an equivalent action, whilst a washer I! may also be provided. By means of the spring II the co-emcient of heat expansion between the insulator body and the electrode are washer l3, for example of asbestos or the like.

The purpose of the washer, in addition to eil'ecting packing, is also to prevent breaking open of the lower end of the insulator root. This would be liable to occur easily when, in consequence of heating, the radiallyexpanding collar 4 acts directly on the insulator foot, with the result that radially directed forces may occur in the insulator foot. Consequently it is advisable to insert the packing disc which, by reason of the change of shape on its lower surface, is capable of following the radial expansion of .the collar 4, whilst the internal resistance to deformation of the insertion must be so slight that the forces transmitted to the top side of the insertion are less than the allowable radial tension of the insulator foot. It is advisable to provide the collar 4 with an undercut as shown in Figure 2.

. In the foot I of the plug body, provided with a screw thread, there is a bore for the. reception of the mass electrode 9. This mass electrode consists of a member 9 which, for example, is mounted on ans-rm II which is enlarged conically out-' wards and then passes into a cylindrical portion I! which engages with a corresponding hole of the foot 8. Opposite to the hole provided for the reception of the cylindrical part 15 of the mass electrode there maybe provided a further hole 26 in the foot of the plug body.

Immediately above the mass electrode 9 and within the lower part of the central electrode 2, there is provided a recess 2a, this recess forming a chamber which communicates by means of an annular space with the cylinder chamber proper. It will be understood, therefore, that this recess 2a. forms what may be termed an auxiliary gas expansion chamber, or a gas extension chamber, which appears to have the following action in practice. The chamber 20. in addition to the chamber 9a in the mass electrode will be hereinafter referred to as the gas extension chamber.

when, for example, in the case of a four stroke engine the piston passes downwardly during the suction stroke, the mixture passes into the cylinder chamber and into the gas extension chamber. When the piston moves upwardly for the purpose of compression, the mixture is compressed in both chambers. In the actual cylinder chamber there are located in the vicinity of the piston the heaviest moist particles of fuel and above these light combustible products. As the compression of the mixture involves heating and the heating is the more intense the less moist cooling mixture particles are present, the heating in the upper part of the cylinder is greater than in the lower part and particularly high in the gas extension chamber in which the combustion air is entirely free from moist particles by reason of the paths of flow. Consequently there obtains, during the entire combustion stroke, in the gas extension chamber a higher pressure than in the actual cylinder chamber, that is to say, the gas extension chamber, during the compression stroke, blows continuously into the actual cylinder chamber with a certain excess pressure. When now during the upward movement of the piston a particle of oil is projected on the electrodes it is either entirely prevented from coming into contact with the electrodes, and thus forming a short-circuit, by the gases blown through the annular gap, or the oil particle comes into contact with the electrodes but is blown off directly at the same moment so that the formation of a short-circuit oil film between the central electrode and the mass electrode is prevented and ignition can take place during or after reaching the upper dead-centre position of the piston. As the gases which flow through the annular gap between the central and mass electrodes are particularly hot and particularly easily explodable these are particularly readily ignited by the passing spark and projected in the form of an annular cutting flame outwardly over the spherical mass electrode and thus isnite the other gas mixture located in the actual cylinder chamber. As. the gap no longer ignites the actual cylinder mixture but ignites the particularly readily explodable mixture flowing from the gas extension chamber and this mixture forms an annular cutting flame, the ignition velocity in the cylinder itself is also increased as the annular cutting flame-like ignited mass has a greater ignition effect than the spark which passes.

The circumstances which have been set out therefore cause, even in the case of cold plugs, that is to say when starting, an intensive ignition and a more efficient utilization of the mixture. When the electrodes, after a predetermined time of action, have reached the working temperature the ignition property of the plug is still further increased in that the mixture in the gas extension chamber is from the start hotter, by reason of being heated by the electrodes, than the mixture located in the cylinder chamber so that the pressure excess of the gases in the gas extension chamber relatively to the actual cylinder chamber and thus the blowing outwardly from the gas extension chamber are further amplified.

To the heating of the mixture in the gas extension chamber by the heating action of the electrodes there must also be added, as above described, the heating as a result of the compression so that also in operation, that is to say when the electrodes have reached the working temperature, there obtains a constant excess pressure in the gas extension chamber relatively to the cylinder mixture and thus any bridging of the spark gap by oil and soot particles is prevented.

Even in the case of stoppage of the engine for any reason should oil or carbon particles have been deposited on the electrodes these will be blown from the electrode surfaces when starting the engine at the latest during the second compression stroke prior to the ignition period so that at the latest the second ignition can take-place unhindered. Thorough researches have shown that the above mentioned results actually occur in fact and most probably are caused by the explanations set out above, whilst it is not impossible that also other factors play a part. The above explanations only relate to the explanation of the apparently most important point of view of the method of operation of the ignition plug.

In Figures 1 and 2 is shown a plug construction wherein the mass electrode 9 consists of a solid ball and only the central electrode 2 is provided with a recess which forms the gas extension chamber. The arrangement may, however, also be such, as shown in Figure 3, namely that the mass electrode 9 is also provided with a recess 9a so that the gas extension chamber is located both'in the central electrode and in the mass electrode. In certain forms of constructicr gas extension chamber is provided therein alone.

The mass electrode may be so arranged opposite the central electrode that the mass electrode lies along the axial extension of the central electrode.

trode and in the mass electrode, for example by providing recesses in the balls of the mass elec trodes as shown in Figure 3.

Figure 5 shows the lower end of an ignition plug wherein the oppositely disposed edges of the central electrode l9 and the mass electrode 20 are provided with sharp edges for facilitating the passage of the spark. In this case the mass electrode 20 is provided on an arm 22 pressed from a ring 2|. The ring 2| is fitted into a suitable groove of the foot 8 of the plug body.

As shown in Figure 1 the central electrode 2 is mounted in a hollow space of the insulator which is larger, by an amount necessitated by tolerance, than the external diameter of the central electrode. In the vicinity of its lower edge the central electrode is centered by a ring 23. This ring, in order to prevent the transmission of heat from the insulator foot to the central electrode, may be constructed from a material which is a poor conductor of heat.

In the insulator body there are formed by milling, pressing or the like cooling ribs 24 and in the surrounding part of the plug body 6 there are provided openings 25 th ough which cooling air reaches the insulator. foot of the plug body from unnecessarily heating the foot of the insulator there may be fitted between the foot of the insulator and the foot of the plug an insertion of poor'heat conducting material, for example asbestos.

the mass electrode may also be so arranged thattn'e The arrangement may also be such that for example two or four spherical In order to prevent the (ill What I claim is: I 1. A sparking plug comprising a plug body, an insulator body, a carrier at the lower end of said plug body, an orifice in said carrier, a rod shaped chamber for a portion of the gases and a recess in said spherical mass electrode to form a gas extension chamber. 4

2. A sparking plug comprising aplug body, an insulator body mounted in said plug body, a rodshaped central electrode mounted in said insu- Jator body, a collar on said central electrode, said collar having an undercut recess therein adjacent the insulator body and bearing against said insulator body, said rod having a reces in the end thereof, a spherical earth electrode mounted in said plug body, said spherical electrode being 10- sulatorbody,saidrodhavingarecessintheendthereof, a spherical earth electrode mounted in said plug body. said spherical electrode being located opposite the recess in said elec- 'trode, said spherical electrode having a recess. therein, said recess being located opposite the recess in thecentral electrode.

4. A sparking plug comprising a plug body, an insulator body mounted in said plug body, a rollshaped central electrode mounted in said insu lator body,a collar on said central electrode, said collar having an undercut recess therein adjacent the insulator body and bearing against said insulator body, said rod having recesses near the end thereof, and a plurality of spherical electrodes mounted in said plug body, said spherical electrodes being located one opposite each recess in the said central electrode.

5. A sparldngplug comprising a plug body, an insulator body mounted in said plug body, a rodsbap'ed central electrode mounted in said insulator body, acollar on said central electrode, said collar having an undercut recess thereinadjacent the insulator body and bearing against said insulator body, said rod having receses near the end thereof, and a plurality of spherical electrodes mounted in said plug body, said spherical electrodes being located one opposite each recess in the said central electrode, each of said spherical electrodes having a recess therein, the recesses in said spherical electrodes being located opposite the recesses in the central electrodemom. 

